title: Effects of material morphology on the phototoxicity of nano-TiO2 to bacteria.
abstract: Nanostructured titania (nano-TiO2) is produced in diverse shapes, but it remains largely unknown how tuning the morphology of nano-TiO2 may alter its toxicity. Herein, we show that material morphology plays a critical role in regulating the phototoxicity of nano-TiO2 to bacteria. Low-dimensional nano-TiO2, including nanotubes, nanorods, and nanosheets, were synthesized hydrothermally, and their effects on the bacterial viability of Escherichia coli and Aeromonas hydrophila were compared to spherical nanostructures (anatase nanospheres and P25). Results reveal that TiO2 nanotubes and nanosheets are less phototoxic than their rod- and sphere-shape counterparts under simulated solar irradiation. None of the tested nano-TiO2 shows toxicity in the dark. In contrast to their diminished phototoxicity, however, TiO2 nanotubes and nanosheets exhibit comparable or even higher photoactivity than other nanostructures. Observations by scanning transmission electron microscopy suggest that material morphology influences nano-TiO2 phototoxicity by governing how nano-TiO2 particles align at the bacterial cell surface. Overall, when comparing materials with different morphologies and dimensionality, nano-TiO2 phototoxicity is not a simple function of photocatalytic reactivity or ROS production. Instead, we propose that the evaluation of nano-TiO2 phototoxicity encompasses a three-pronged approach, involving the intrinsic photoactivity, aggregation of nano-TiO2, and the nano-TiO2/bacteria surface interactions.
authors.affiliation: Department of Civil and Environmental Engineering, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208, United States.
authors.forename: Tiezheng
authors.initials: T
authors.lastname: Tong
authors.forename: Anas
authors.initials: A
authors.lastname: Shereef
authors.forename: Jinsong
authors.initials: J
authors.lastname: Wu
authors.forename: Chu Thi Thanh
authors.initials: CT
authors.lastname: Binh
authors.forename: John J
authors.initials: JJ
authors.lastname: Kelly
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Gaillard
authors.forename: Kimberly A
authors.initials: KA
authors.lastname: Gray
mesh_terms: D016980:Aeromonas hydrophila / Q000187:drug effects* / Q000528:radiation effects* / Q000648:ultrastructure; D002384:Catalysis / Q000187:drug effects / Q000528:radiation effects; D004926:Escherichia coli / Q000187:drug effects* / Q000528:radiation effects* / Q000648:ultrastructure; D007700:Kinetics; D008027:Light; D050296:Microbial Viability / Q000187:drug effects / Q000528:radiation effects; D049329:Nanostructures / Q000633:toxicity* / Q000648:ultrastructure; D013052:Spectrometry, X-Ray Emission; D014025:Titanium / Q000633:toxicity*
chemical_list: C009495:titanium dioxide; D014025:Titanium